123 chassis wipers only on High - PeachParts Mercedes-Benz Forum

NCfriend · #1 05-05-2009, 01:37 PM

Again I appeal to the MB masses for helping this novice and his 1981 300 TD.
My wipers progressively quit responding to the low and med settings. They never fail on high, but I could leave them in low position and they only randomly swish, even stopping mid stroke - he he
Now, no response on low or med; high or nothing at all.

Any experience with this? Is it electrical, the motor, the handle switch, or some relay?

If you have an idea what may cause this problem; please advise how to properly get this part off. I have a donor that should supply test replacements.

thanks for reading

300SD81 · #2 05-05-2009, 01:41 PM

I had a similar problem, try cleaning out the wiper relay.

NCfriend · #3 05-05-2009, 01:44 PM

I located the relay and switched with a donor if any better;
Still no intermittent settings, and I cannot hear any clicking from the relay.
Are both relays bad?
One of the relay tips had black scaring = short somewhere?

turn signals and high beams good. The washer sprays but does not engage the wiper either...
Seems like no power signal coming to the relay at these settings, which might mean the control/signal arm?

If the arm control is the problem, how do you get into it and check???

anything work best for cleaning relays besides blowing hard?

NCfriend · #4 05-05-2009, 08:41 PM

So it was the control in the steering column arm!
I thanked my wife for allowing me the parts car; then fairly easily removed the entire control unit with cruise and turn signal arms from the column of the donor. Plugged it into my wagon and all settings work normal

If anyone reading this would like the basic directions for removing that part just ask...
Not sure why is was bad. Frustrating, but easy fix in the end. If anyone wants the old unit for the price of S&H I'll let you play with it.

I think it might have fried the relay also by the black scarred tips? Good place to start. It was the one small silver relay on top of the column, directly behind the cluster.

Thanks for the support

techguy512 · #5 05-05-2009, 09:43 PM

Quote:

Originally Posted by NCfriend

I think it might have fried the relay also by the black scarred tips? Good place to start. It was the one small silver relay on top of the column, directly behind the cluster.

Thanks for the support

The relay only has 3 functions:

1) Fixed duration intermittent wiping
2) "wipe after wash" function (5 seconds of wiping after the washer pump disengages)
3) provides a return path for current so that the wipers auto-park

Did your intermittent function return when you changed your stalk switch? If not the relay might be damaged. I can repair it using a little microprocessor circuit I designed that adds a "programmable" intermittent feature. You can adjust the wiper delay on-the-fly all the way out to 30 seconds. Plug and play, no wiring or switch mods.